Phreatic surface measurers are generally known as instruments used to measure water levels (within piezometers, wells, tanks, etc.), the knowledge of which are important in various research fields, such as geotechnics, hydrology, and more generally, environmental studies.
Phreatic surface measurers generally include four main components:                a winding system;        a tape measure;        a data detection and display system; and        a terminal (or sensor(s)).        
Generally, a winding system can include a bobbin, with a winding mechanism, such as a handle mounted on a support frame, for example and not in limitation. A bobbin body can provide various measurement electronics, including circuitry, a communication system for communicating measured parameters, and a power source, such as a battery, for example and not in limitation. A support frame can further include a friction/blocking system for the bobbin, to adjust its sliding and for housing the terminal when not in use.
A tape measure can generally include electrical wires, connecting the electronics and/or circuitry to one or more sensors provided at the terminal, and a detection and/or processing apparatus. The tape also provides a support core, which is flexible but resistant to bending stresses.
A necessary requirement of measuring tapes can be that of providing a negligible lengthening without plastic deformations when subjected to even remarkable traction stresses.
Measure tapes usually have a circular section with a diameter ranging between 4 and 5 mm, and made up of rubber, thus efficiently protecting the inner electrical wires. KEVAR is presently widely used for the wire resistant core, whilst anti-scratch polyurethane is widely used for the outer sheath.
Despite rubber being a very resistant and flexible material, its use is often inconvenient, as it creates remarkable friction. This creates significant drawbacks when carrying out measurement operations, mainly at the ends.
A terminal is the component that is connected to the free end of a tape measure, and has the one or more sensors built-in. Main features a terminal must generally possess are the following:                a sufficient weight to maintain the tape measure in a straight orientation;        the presence of openings (such as holes or slits) close to the sensor to allowing the exit of water from the sensor when withdrawing the terminal from water, and the existence of an electrical bridge that would prevent quick measurements (for example, that which can be necessary for measuring a dynamic level during the withdrawal from a well);        being comprised of a suitable material to avoid chemical contamination with water with which it is in contact.        
A data detection and display system can include electrical or electronic apparatuses provided with suitable optical and sound signaling mechanisms.
Terminals presently available on the market differ in their respective structures and the types of sensors employed.
For example, some terminals employ piezometers as measurement instruments, and can structurally include tubes (usually PVC tubes) provided within drillings made within the ground, and with holes or slots allowing the inflow and outflow of stratum water.
From a structural perspective, a terminal can be represented, in its simplest form, as a metallic tubular body housing electrical wires, and providing a sensor on its free end.
In order to permit the measurement of water levels, electrical circuits are usually employed, and generally include a power supply, a current flowing passage, and a switch provided on the lower end of the terminal (the sensor), which uses the conductive properties of water for electrically closing the circuit.
Many phreatic surface measurer models, in order to give the opportunity of measuring other desired parameters, provide the above technical scheme integrated with other types of sensors, such as the following:                sensors for measurement of water temperature (thermo-phreatic surface measurers);        pH measurement sensors; and        sensors for measuring electrical conductivity.        
Often, however, there is a need for measuring piezometers, static and/or dynamic levels within wells equipped for water drawing, for example, wells provided with filters, a pump, a motor, an inlet conduit with relevant spacers from the coating (if provided), and motor supply cables. This occurs frequently, as most existing wells, mainly those for private use or for drawing small amounts of water, do not include piezometers due to cost limitations.
Presently known measurers suffer from at least the following drawbacks:                The terminal can meet an obstacle, often being an inlet conduit spacer. In this case, the halting of a phreatic surface measurer terminal's advancement cannot be timely revealed to the operator at the surface, with the operator continuing to unwind the bobbin until the progressive reduction of tension makes the situation evident. Also, the subsequent re-winding of the cable about the bobbin, which is necessary to repeat the attempt of lowering the instrument, can be precluded by the winding of the tape measure around projections that could be present (such as spacing brackets, bolts and nuts, etc.), or by the formation of a tape measure skein knotted about the phreatic surface measurer terminal, and thus preventing the terminal from passing through narrow spaces.        The descent and ascent of the terminal assembly, plus the oscillations of the same about the vertical axis, can cause its wrapping around an obstacle, such as a water inlet conduit and/or electrical wires supplying power to a pump motor. Attempts to free the terminal from such conduits are difficult due to the reduced space available and due to the friction of the tape with such obstacles, and further can be hindered, or even completely precluded, by the presence of projections, bolts and nuts, brackets, etc., or by couplings between a conduit and wires, where the terminal can be effectively fixed thereto indefinitely.        
It is clear that the above procedure is quite inefficient both cost-wise and time-wise due to the various problems addressed above. Indeed, often measurer operators lose at least a portion of the measurer itself, leaving the same within the well, and resulting in significant damage to the measurer.